In the past, techniques for reducing engine noise flowing into a cabin of a vehicle for quietness of driving of the vehicle were mainly applied. However, in the recent years, techniques for amplifying engine sounds in various types are implemented in order to realize dynamic and sporty driving sound to be heard inside the vehicle.
The sound amplifying ways may be divided into three types: a membrane sound generator type; an electric sound generator type; and an active sound generator type.
The membrane sound generator type is configured such that a membrane is mounted on a dash panel, that is, a partition member separating an engine room from the cabin of the vehicle, and a pipe is connected between an engine intake side and the membrane so that engine discharge sound is directly transmitted to the cabin of the vehicle through the membrane. The membrane sound generator type has an advantage of realizing a natural tone by transmitting the engine discharge sound directly to the cabin of the vehicle; however, it cannot tune the engine discharge sound to desired frequency, and thus cannot realize a desired sound.
The electric sound generator type is configured so that when a dash panel becomes excited using a separate actuator, sound due to the excitation is transmitted to the cabin of the vehicle. The electric sound generator has an advantage of being capable of tuning the engine discharge sound to a desired frequency band, but rattle noise occurs and durability of the dash panel is decreased according to direct excitation of dash panel.
The active sound generator type is configured to arbitrarily generate sound such as the engine sound from a speaker inside the vehicle. The active sound generator type has an advantage of being capable of tuning the engine discharge sound to the desired frequency band. However, it is difficult for a user to feel the sound because the active sound generator type does not have vibration such as in the case of electric sound generator type, and feel a sense of difference from natural tone as the sound gives the user artificial sensibility rather than natural tone.